The amylin family of peptide hormones, including amylin, calcitonin, calcitonin gene related peptide (CGRP), adrenomedullin (ADM), and intermedin (also known as “AFP-6”) is a family of peptide hormones generally implicated in metabolic conditions and disorders. It has been reported that the biological actions of amylin family peptide hormones are generally mediated via binding to two closely related type II G protein-coupled receptors, the calcitonin receptor (CTR) and the calcitonin receptor like receptor (CRLR). Cloning and functional studies have shown that, CGRP, ADM, and amylin interact with different combinations of CTR or the CRLR and the receptor activity modifying protein (RAMP). It is believed that co-expression of RAMPs and either the CTR or CRLR is required to generate functional receptors for calcitonin, CGRP, ADM, and amylin. A specific receptor for AFP-6 has not been reported; however, binding studies indicate that AFP-6 binds to all the known receptors of the amylin family.
In general, amylin regulates gastric emptying, and suppress glucagon secretion and food intake, thus regulating the rate of glucose appearance in the circulation. In human trials, an amylin analog, pramlintide, has been shown to reduce weight or weight gain. Amylin may be beneficial in treating metabolic conditions such as diabetes and obesity. Amylin may also be used to treat pain, bone disorders, gastritis, to modulate lipids, in particular triglycerides, or to affect body composition such as the preferential loss of fat and sparing of lean tissue. See, for example, U.S. Pat. Nos. 5,175,145, 5,677,279, 5,405,831, 6114,304, and U.S. Pat. Application Publication Nos. 2002-0010133, 2003-0130177, 2004-0022807, and 2005-0197287.
The hormone calcitonin (CT) was named for its secretion in response to induced hypercalcemia and its rapid hypocalcemic effect. CT has an effect on plasma calcium levels and inhibits osteoclast function and is widely used for the treatment of osteoporosis. Therapeutically, salmon CT (sCT) appears to increase bone density and decrease fracture rates with minimal adverse effects. CT has also been successfully used over the past 25 years as a therapy for Paget's disease of bone, which is a chronic skeletal disorder that may result in enlarged or deformed bones in one or more regions of the skeleton. CT is also widely used for its analgesic effect on bone pain experienced during osteoporosis, although the mechanism for this effect is not clearly understood.
Calcitonin gene related peptide (CGRP) is a neuropeptide whose receptors are widely distributed in the body, including the nervous system and the cardiovascular system. This peptide seems to modulate sensory neurotransmission and is one of the most potent endogenous vasodilatory peptide discovered to date. Reported biological effects for CGRP include: modulation of substance P in inflammation, nicotinic receptor activity at the neuromuscular junction, stimulation of pancreatic enzyme secretion, a reduction of gastric acid secretion, peripheral vasodilation, cardiac acceleration, neuro-modulation, regulation of calcium metabolism, osteogenic stimulation, insulin secretion, an increase in body temperature and a decrease in food intake (Wimalawansa (1997) Crit. Rev Neurobiol. 11:167-239).
Adrenomedullin (ADM) is almost ubiquitously expressed with many more tissues containing the peptide than not. Hinson et al. (2000) Endocrine Reviews 21:138-167 details effects of ADM on the cardiovascular system, cellular growth, the central nervous system and the endocrine system, with a range of biological actions including vasodilation, cell growth, regulation of hormone secretion, and natriuresis.
Expression of AFP-6 (i.e., intermedin) is primarily in the pituitary and gastrointestinal tract. In in vivo studies, AFP-6 administration led to blood pressure reduction in both normal and spontaneously hypertensive rats and in vivo administration of AFP-6 in mice led to a suppression of gastric emptying and food intake (Roh et al. (2004) J. Biol. Chem. 279:7264-7274.)
It is estimated that about 64% of Americans are overweight or obese (roughly about 97 million adults) and it is generally believed that these numbers are increasing. Being obese or overweight may substantially increase the risk of morbidity from hypertension; dyslipidemia; type 2 diabetes; coronary heart disease; stroke; gallbladder disease; osteoarthritis; sleep apnea and respiratory problems; and endometrial, breast, prostate, and colon cancers. Higher body weights are also associated with increases in all-cause mortality. Furthermore, being obese or overweight may cause a person to have negative self-image about him or her self.
In humans, patients who are overweight or obese are considered those with a Body Mass Index (BMI) of equal or greater than 25. BMI is a common measure expressing the relationship (or ratio) of weight-to-height. It is a mathematical formula in which a person's body weight in kilograms is divided by the square of his or her height in meters (i.e., wt/(ht)2). Individuals with a BMI of 25 to 29.9 are considered overweight, while individuals with a BMI of 30 to 39.9 are considered obese, and individuals with a BMI of 40 or more are considered morbidly obese. According to the NIH Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, all adults (aged 18 years or older) who have a BMI of 25 or more are considered at risk for premature death and disability as a consequence of overweight and obesity. These health risks increase even more as the severity of an individual's obesity increases.
For these reasons, there is an enormous interest in treating obesity. Existing therapies include standard diets and exercise, very low calorie diets, behavioral therapy, pharmacotherapy involving appetite suppressants, thermogenic drugs, food absorption inhibitors, mechanical devices such as jaw wiring, waist cords and balloons, and surgery, such as gastric bypass. Jung et al. (1991) Clinical Endocrinology 35:11-20; Bray (1992) Am. J. Clin. Nutr. 55:538 S-544S.
In general, however, while loss of fat is desired, loss of lean body mass (protein) is not. Lean body mass is highly active metabolically and physiologically and the size is generally genetically defined and maintained. Lean body mass contains all the body protein. There is no real protein store as every protein molecule has a role in maintaining homeostasis. It is believed that loss of body protein is deleterious to the health of an individual. The majority of the protein in the lean body mass is in the skeletal muscle mass. Lean body mass is 50-60% muscle mass by weight, the rest is bone and tendon. Protein makes up the critical cell structure in muscle, viscera, red cells and connective tissue. Enzymes, which direct metabolism, and antibodies, which maintain immune function, are also proteins. Thus, it is desirable to prevent or minimize loss of lean body mass even while reducing body fat.
Caloric restriction, regardless of its form, can cause catabolism of body protein and produce negative nitrogen balance. Protein-supplemented diets, therefore, have gained popularity as a means of lessening nitrogen loss during caloric restriction. Protein-sparing modified fasting has been reported to be effective in weight reduction in adolescents. Lee et al. (1992) Clin. Pediatr. 31:234-236. However, these diets may produce only modest nitrogen sparing. A need exists for effective ways of promoting fat loss yet preserving lean body mass or minimizing its loss.
Eating is controlled by many factors, including appetite, food availability, family, peer, and cultural practices, and attempts at voluntary control. Dieting to a body weight leaner than needed for health is highly promoted by current fashion trends, sales campaigns for special foods, and in some activities and professions. Eating disorders involve serious disturbances in eating behavior, such as extreme and unhealthy reduction of food intake or severe overeating, as well as feelings of distress or extreme concern about body shape or weight. Researchers are investigating how and why initially voluntary behaviors, such as eating smaller or larger amounts of food than usual, at some point move beyond control in some people and develop into an eating disorder. Studies on the basic biology of appetite control and its alteration by prolonged overeating or starvation have uncovered enormous complexity, but in the long run have the potential to lead to new pharmacologic treatments for eating disorders.
The main types of eating disorders are anorexia nervosa and bulimia nervosa. A third type, binge-eating disorder, has been suggested but has not yet been approved as a formal psychiatric diagnosis. Eating disorders frequently develop during adolescence or early adulthood, but some reports indicate their onset can occur during childhood or later in adulthood. Eating disorders frequently co-occur with other psychiatric disorders such as depression, substance abuse, and anxiety disorders. In addition, people who suffer from eating disorders can experience a wide range of physical health complications, including serious heart conditions and kidney failure which may lead to death. Recognition of eating disorders as real and treatable diseases, therefore, is critically important.
There remains a need for effective methods and compositions for modifying body composition as well as controlling, preventing or treating obesity and eating disorders and associated conditions and disorders.
All patents, patent applications, and publications cited herein are hereby incorporated by reference in their entirety.